Receptacles – Sidewall structure – Having an outlet or inlet opening
Reexamination Certificate
2000-02-23
2001-08-21
Pollard, Steven (Department: 3727)
Receptacles
Sidewall structure
Having an outlet or inlet opening
C220S495040, C215S012100, C264S155000, C264S156000, C264S512000, C264S513000
Reexamination Certificate
active
06276558
ABSTRACT:
The present invention relates to a method of producing a receptacle consisting of a substantially stiff outer receptacle and an easily deformable inner bag which are made from respectively different thermoplastic materials that do not form a welded joint with one another, said receptacle comprising a receptacle opening and at least one wall opening provided in the outer receptacle, through which pressure is compensated in the area between the inner bag and the outer receptacle, with a parison, which consists of at least two tubings, being coextruded and arranged between the opened halves of a blow mold, and the blow mold being closed when said parison has reached the length required for producing the receptacle, the bottom area of the receptacle to be produced having formed therein an outwardly projecting web made of welded material of said outer receptacle, in which web the welded bottom seam of the inner bag is clamped and held in axial direction, and the parison being inflated by a pressure medium for contact with the wall of the blow mold and removed from the blow mold. Furthermore, the present invention relates to such receptacles having at least one pressure compensating opening.
A method of the type in question is disclosed in DE 41 39 555 C2. The closed and at least partly welded bottom seam of the outer receptacle is formed by shaping the squeeze area of the blow mold at the bottom side in a special manner, with excess material being squeezed off and material of the outer receptacle being united at both sides to form a web of an approximately kite-shaped cross-section from which the welded bottom seam of the inner receptacle slightly recedes towards the interior of the receptacle due to the impact pressure built up in the cavity forming the web, so that the material of the outer receptacle is welded together over part of the web. The weld seam of the inner bag is clamped in the area positioned thereabove. The projecting web provided at the bottom of the outer receptacle may also have a different cross-sectional shape, for instance an arched shape.
As for the formation of the welded bottom seam of the outer receptacle and the clamping of the weld seam of the inner bag provided at the bottom side, explicit reference is here made to the content disclosed in DE 41 39 555 C2.
A pump for discharging the receptacle contents received in the inner bag may be provided on the receptacle opening of the receptacle of the type in question. However, the receptacle may also be a squeeze-type receptacle in the case of which the outer receptacle is squeezed by hand for discharging the receptacle contents to subsequently assume its initial shape again.
In the receptacle which is known from DE 41 39 555 C2, pressure compensation which becomes necessary due to a decrease in volume of the inner bag, which has been caused by the discharge of the receptacle contents, is carried out with the aid of unwelded shoulder seams of the outer receptacle which are formed in that the coextruded blank has a diameter which is greater than the neck portion of the blow mold, so that the blank is squeezed off in the shoulder portion and on the neck of the receptacle to be produced when the blow mold is closed for eliminating excess material. This is done without the formation of an outwardly projecting web as in the case of the bottom seam so that, during the smooth squeeze-off operation in the squeeze area of the shoulder portion and of the neck portion, material of the inner bag remains between the spaced-apart material of the outer receptacle, so that the last-mentioned material cannot be welded together, since the material of the inner bag does not recede. Hence, a closed weld seam is formed on the inner bag and ensures a leakage-proof inner bag, and air can enter through the shoulder seams of the outer receptacle, which are open at both sides, from the surrounding atmosphere for pressure compensation.
This configuration has the disadvantage that, starting from the open shoulder seams of the outer receptacle, the receptacle consists of two shells which rest on one another in a substantially loose manner. When the receptacle is equipped with a pump and when the pump is put on the two neck halves in a slightly inclined manner, the two shells may get slightly displaced relative to one another, whereby a step is formed on the upper edge, as a result of which the receptacle is no longer leakproof, since even a rubber insert provided at this place could not compensate for the resulting unevenness. Moreover, only receptacles with shoulder sections can be provided in the known manner with the open pressure compensating seams, whereas in the case of so-called wide-necked vessels, which are devoid of any shoulder sections, no pressure compensating openings can be formed in this way.
EP-A-0 759 399 discloses a method according to the preamble of patent claim
1
. The document suggests that a hole should be punched out of the wall of the outer receptable my means of a sharp circular cutting tool in that said cutting tool is pressed through the wall of the outer receptacle. There is the risk that the inner bag may get damaged.
It is the object of the present invention to provide a method with the aid of which in receptacles of the type under consideration pressure compensating openings can be produced in the wall of the outer receptacle in a different way than in the one offered by unwelded shoulder seams, without any leakage problems arising therefrom in the receptacle.
It is also an object to indicate a receptacle which includes at least one pressure compensating opening in its outer receptacle without the above-mentioned drawbacks being observed.
These objects are achieved by the features of patent claims
1
and
12
.
Advantageous developments of the present invention are characterized in the dependent claims.
According to the present invention at least one wall opening of the outer receptacle is formed subsequent to the blow molding process in that a preferably convex wall section is cut away from the wall of the outer receptacle in such a manner that a hole is formed in the outer wall. This means that the outer wall, which the very thin, flexible inner bag rests on, is cut away completely at least in a very small portion without the inner bag being damaged thereby. This is surprising for the reason that the cutting tool which cuts away the wall section of the outer receptacle also hits on the inner bag during its cutting operation, which necessarily follows already from the fact that a certain wall surface which, among other things, depends on the size of the receptacle and the number of the wall openings must be cut away completely to form the hole in the outer receptacle. Moreover, tolerances in the wall thickness of the outer receptacle are unavoidable, the thickness ranging, for instance, from 1 to 1.5 mm, so that the cutting depth has to be set in practice in a manner to ensure that a hole leading through the outer receptacle is actually formed by the cutting operation.
Although the sharp cutting tool impinges on the inner bag, which is very thin as a rule and has a wall thickness of e.g. 0.1 to 0.25 mm, this inner bag is not damaged by the cutting tool when the tool impinges on the inner bag at a very flat angle. Since at the moment at which the wall of the outer receptacle is fully severed, air enters into the space between the outer receptacle and the inner bag, the cutting tool presses the flexible inner bag inwards without damaging said bag in a tightness-impairing manner. No wall section is cut away from the inner bag since, as mentioned, the inner bag is pressed away by the cutting tool while the cutting tool continues the cutting operation on the outer receptacle.
Wall openings can thereby be formed virtually at any place of the receptacle on the outer receptacle, with the cutting operation being preferably performed in one direction in which the outer receptacle is curved outwards. This is, for instance, the case with a circumferential wall of a receptacle that has a circular cylindrical shape,
GAPLAST GmbH
Pollard Steven
Pyle & Piontek
LandOfFree
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